No real security issues unless you give away your master key,
Most people use CA certificates for id purposes. Self signed certificates hold no real grounds because they were never verified by a third party CA.
If its just between friends, you don't plan to make it public, and only need basic security, self signed is fine.
If it is large scale, public, sending any sensative data, or needs (standard) security, signed by a CA is usually the way to go.
If you do wish to obtain a signed certificate companies such as StartCom have 100% free CA signed certificates you can use, and if you wanted, severl other companies only charge around 10 dollars per year (unless you go extreeme).